1. Field of the Invention
The present invention relates to a circuit breaker or a circuit protector provided on a power board and more especially relates to a magnetic latch type, no fuse circuit breaker or circuit protector.
2. Description of the Prior Art
Circuit breakers of this kind are generally requested to open an electric circuit quickly and definitely at a time of occurrence of short circuit in order not to damage the circuit breaker itself and also for the devices connected to the circuit through said circuit breaker. There are various suggestions for such a circuit breaker to open the circuit quickly in case of occurrence of circuit trouble. For instance, there have been suggestions using temperature operation of a magnetic latch type device in order to obtain time lag circuit breaking operation based on a thermal demagnetization function and/or an instantaneous circuit breaking operation using an electromagnetic operative function.
The conventional circuit breakers are generally complicated in construction. Contactors of such conventional circuit breakers are either of the self closing type using spring force making its own contact or of the forced contact type using spring force specially provided therefor. The former has a disadvantage in that the spring force of the contactor may make the opening time of breaker longer and the latter also has a disadvantage in that the additional spring to apply bias force to increase the contact force may make the opening time of the breaker longer so that the contact pressure can not be made sufficiently high in both cases. Accordingly, the conventional circuit breakers had generally high contact resistance and there was a fear of damaging the contactor at its current flowing portion by an arc occurring at the time of opening the breaker.
The present invention has for its object to mitigate the aforementioned disadvantages of the conventional devices and to obtain a circuit breaker having a bias spring acting against magnetic latching force which can also act to apply contacting pressure at the time of closing the circuit breaker.
The circuit breaker of the present invention is characterized in that it comprises in combination, a pair of lead terminals, an attracting magnet member having a conductive soft magnetic element of which one end is connected to one of said lead terminals, a stationary contact secured to the other end of said attracting magnet member, a magnet element arranged oppositely against said attracting magnet member, a magnetic latching member holding said magnet element and arranged in a movable manner integrally with the magnet element against said attracting magnetic member, a moving spring assembly pivoted to said magnetic latching member, a moving contact secured at one side of the moving spring assembly with respect to a pivoting shaft and in a position oppositely facing against the stationary contact, which moving contact forms a circuit breaker contact together with said stationary contact, and a bias spring engaged with said moving spring assembly at the other side with respect to the pivoting shaft and acting to apply a bias force to the magnetic latching member together with the magnet element held therein in a direction away from the attracting magnetic member, wherein under the closing condition of the circuit breaker in which the magnet element is attracted to the attracting megnetic member and the moving contact is under contact with the stationary contact, the bias spring applies a pressure to the moving contact toward the stationary contact.